Agreed about the family orientedness - some people just aren't. But I think if Hermione had a sister, or Harry a brother, we'd know. That doesn't mean Remus can't have one. And good point about Kingsley.

As for Harry, yes, definitely second cousins. But I just think if he had another aunt, (especially on the wizarding side), Harry'd have known.

Wow to your Riddle idea - you know, youu're right, too. He was sick enough.